Hi Ahab, welcome to NeoSmart Technologies!
In answer to your question: this is a limitation of Windows, as imposed by Microsoft. At the moment, there is nothing we (as in the EasyBCD Team) can do about this.
Modify boot.ini on the main (boot) drive to include the entries for each of the "Legacy" Windows operating systems.
If you're doing a demonstration, why not make it all the more impressive and add Linux to the mix? EasyBCD makes it even easier to dual-boot Linux and Vista than Microsoft makes it to dual-boot Vista and XP!